Bubble cap assembly

ABSTRACT

A bubble cap assembly is provided with keyways and a special keyed lock washer with locking tabs to securely fasten the bubble cap during operation in a reactor. The unique arrangement also accommodates simple removal for easy maintenance and decoking without damaging the bubble cap assembly.

BACKGROUND OF THE INVENTION

This invention relates to reactors in petroleum refineries and, moreparticularly, to bubble caps for use in reactors.

In ebullated (expanded) bed reactors, hundreds of bubble caps are usedto help provide for uniform flow distribution of the oil feed.Conventional bubble caps are keyed to risers and tack welded or backwelded to cap screws. Periodically, the reactors must be shut down formaintenance and removal of coke buildup.

In order to disassemble or remove conventional bubble caps formaintenance and decoking, it is usually necessary to grind the welds offthe cap screws or, alternatively, remove the cap screws with an impactwrench. Such grinding is very tedious, time consuming, and expensive,particularly since the reactors contain hundreds, and sometimesthousands, of bubble caps. Impact wrenches often create severe torqueswhich can shear the keys and damage the bubble caps. After the bubblecaps are decoked and their associated check valves are cleaned orreplaced, the sheared keys must be repaired or replaced. Such repair andreplacement are very cumbersome, laborious, and expensive. It alsorequires rewelding, such as Heliarc welding with a tungsten inert gas,which may not be effective if there is not enough weld metal to secureand rebuild the keys. Once the keys are restored, rebuilt, and repaired,the cap screws must again be back welded to the bubble caps. Thisprocedure greatly increases the downtime of the reactor and the expenseof maintenance and decreases the profitability of the refinery.

Furthermore, occasionally during operation of the unit, the back weldsof the cap screws will break and the cap screws will unscrew. This canlead to additional shutdown of the reactor, which is very expensive andunde- sirable.

Over the years, a variety of lock washers, lock nuts, and other lockingdevices have been developed. Typifying these prior-art lock washers,lock nuts, and other locking devices are those found in U.S. Pat. Nos.57,132, 76,201, 257,778, 257,788, 281,344, 394,537, 396,691, 405,632,494,338, 514,397, 527,179, 549,529, 608,162, 613,630, 626,271, 753,415,858,549, 860,758, 873,424, 923,264, 929,827, 950,123, 950,282, 968,991,970,274, 982,763, 1,033,759, 1,041,832, 1,077,080, 1,089,175, 1,130,851,1,202,893, 1,208,620, 1,235,717, 1,287,371, 1,288,482, 1,308,505,1,333,529, 1,378,116, 1,382,306, 1,578,160, 1,598,165, 1,617,914,1,634,744, 1,707,931, 1,733,529, 1,816,192, 1,881,935, 1,896,650,1,898,801, 1,934,972, 1,951,228, 1,552,681, 2,031,530, 2,290,056,2,374,403, 2,384,668, 2,950,944, 3,318,355, 3,421,563, and 4,286,807.These prior-art lock washers, lock nuts, and locking devices have metwith varying degrees of success. None of these lock washers, lock nuts,and locking devices, however, have been used with bubble caps.

It is, therefore, desirable to provide an improved bubble cap assemblywhich overcomes most, if not all, of the preceding problems.

SUMMARY OF THE INVENTION

An improved bubble cap assembly is provided for use in reactors of oilrefineries. Advantageously, the novel bubble cap assembly is readilyassembled without welding, is securely locked during use in the reactor,and is easy to disassemble and maintain. Desirably, the novel bubble capassembly minimizes downtime and maintenance expenses, significantlyimproves the profitability of the unit, and is easy to install and use.The unique bubble cap assembly is also efficient, effective, andreliable.

To this end, the novel bubble cap assembly has a tubular riser with anotch that provides a riser keyway. The tubular riser provides forpassage of oil upwardly in the reactor. A bubble cap is seated upon theriser in an umbrella- or mushroom-like manner to radially distribute theflow of oil in the reactor. The bubble cap has a specially designed slotwhich provides a bubble cap keyway that is aligned with the riserkeyway.

Mounted on the bubble cap is a unique keeper. The unique keepercomprises a specially designed lock washer with at least one bendablelocking tab or tang and a key which lockably engages and securelyconnects the bubble cap keyway and the riser keyway. A cap screw, bolt,or other fastener is connected to the riser and secured to the keeper.Advantageously, the locking tab of the keeper is of a size and shape andhas sufficient mechanical strength to abuttingly engage and securelylock the head of the fastener to prevent rotation and removal of thefastener during operation of the reactor.

In the preferred form, the key and bubble cap keyway are substantiallylonger than the riser keyway to provide sufficient strength and materialto weld the key to the bottom surface of the keeper. The keeperpreferably has an enlarged arcuate support surface, segment, or basewhich is seated against and welded to the key in order to enhance theload-carrying strength and rigidity of the key.

A more detailed explanation of the invention is provided in thefollowing description and appended claims taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an assembly view of the bubble cap assembly and keeper inaccordance with principles of the present invention;

FIG. 2 is a perspective view of the bubble cap assembly afterinstallation;

FIG. 3 is a cross-sectional schematic view of a reactor containing theinstalled bubble cap assemblies;

FIG. 4 is an enlarged cross-sectional side view of the bubble capassembly taken substantially along line 4-4 of FIG. 2;

FIG. 5 is a top view of the bubble cap;

FIG. 6 is a top view of the riser;

FIG. 7 is a top view of the keeper with one of the locking tabs bentafter installation;

FIG. 8 is a top view of the bubble cap assembly;

FIG. 9 is a perspective view of the keeper;

FIG. 10 is a top view of the keeper prior to installation; and

FIG. 11 is a bottom view of the keeper.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 3, high-sulfur resid oil feed, also referred to assour crude or vacuum-reduced crude, comprising 1000° F. resid and heavygas oil, is fed into a resid hydrotreating unit (RHU) 10 along with ahydrogenrich feed gas. The resid hydrotreating unit comprises a seriesor set of ebullated (expanded) bed reactors 12. In the reactors, theresid is hydroprocessed (hydrotreated) in the presence of fresh and/orequilibrium hydrotreating catalyst and hydrogen to produce an upgradedeffluent product stream leaving used spent catalyst. Hydroprocessing inthe RHU includes demetalation, desulfurization, denitrogenation, residconversion, oxygen removal (deoxygenation), and removal of Rams carbon.

The oil feed typically comprises resid oil (resid) and heavy gas oil.The feed gas comprises upgraded recycled gases and fresh make-up gases.Demetalation primarily occurs in the first ebullated bed reactor.Desulfurization occurs throughout the ebullated bed reactors. Theeffluent product stream typically comprises light hydrocarbon gases,hydrotreated naphtha, distillates, light and heavy gas oil, andunconverted hydrotreated resid. The hydrotreating catalyst typicallycomprises a hydrogenating component on a porous refractory, inorganicoxide support.

The resid hydrotreating unit is quite flexible and, if desired, the samecatalyst can be fed to one or more of the reactors or a separatedemetalation catalyst can be fed to the first reactor while a differentcatalyst can be fed to the second and/or third reactors. Alternatively,different catalysts can be fed to each of the reactors, if desired. Theused spent catalyst typically contains nickel, sulfur, vanadium, andcarbon (coke).

As shown in FIG. 3, the fresh hydrotreating catalyst is fed downwardlyinto top of the ebullated bed reactor 12 through a fresh catalyst feedline 14. Hot resid feed containing resid oil and heavy gas oil is fedthrough a resid feed line 16 and mixed with hydrogen-containing feedgases from a feed gas line 18 in a common oil-gas feed line 20. The oiland gas feed is directed upwardly in a uniform distribution by anannular feed distributor and header 22 in the lower portion of thereactor 12. The oil and gas flows upwardly through a distributor plateor grid 24 into the catalyst bed 26. The distributor plate or grid 24comprises a bubble tray 28 and contains numerous bubble cap assemblies30 which help distribute the oil and gas across the reactor 12 andprevent catalyst from falling into the bottom section of the reactor. Anebullating pump 32 circulates oil from a recycle pan 34 through adowncomer 36 and the distributor plate 24. The rate is sufficient tolift and expand the catalyst bed from its initial settled level to itssteady state expanded level. The effluent product stream of partiallyhydrotreated oil and hydrogen-rich reactor tail gases (off gases) iswithdrawn from the reactor through effluent product line 38. The usedspent catalyst is withdrawn from the bottom of the reactor through spentcatalyst discharge line 40. The spent catalyst typically containsdeposits of metal, such as nickel and vanadium, which have been removedfrom the influent feed oil (resid) during hydrotreating.

Catalyst particles are suspended in a three-phase mixture of catalyst,oil, and hydrogen-rich feed gases in the reaction zone of the reactor12. Hydrogen-rich feed gases typically continually bubble through theoil. The random ebullating motion of the catalyst particles results in aturbulent mixture of the phases which promotes good contact mixing andminimizes temperature gradients.

As shown in FIGS. 1, 2, and 4, each bubble cap assembly 30 has avertically elongated tubular riser 42, a bubble cap 44, an annularkeeper 46 comprising a lock washer, and a fastener 48, such as a capscrew or bolt.

The riser 42 extends upwardly in the reactor. The riser can be milledand fabricated from a piece of pipe. The riser has an annular tubularside wall 52 which is positioned about an axial (vertical) flowpassageway and opening 54. The lower portion 56 of the riser 42 has anaxial inlet opening and mouth 58 (FIG. 4) for ingress of the oil and gasfeed. Preferably, the lower portion 56 of the riser 42 has a set ofupwardly extending, elongated inlet slots 60 and 62 in communicationwith the axial flow passageway 54 to help receive the influent oil andgas feed. The inlet slots 60 and 62 are positioned below an annularflange 64. The annular flange 64 extends diametrically outwardly fromand is welded to the side wall 52 to support the bubble tray 28. Theannular flange 64, riser 42, and axial flow passageway 58 have acircular cross-sectional area.

The upper portion 66 of the riser 42 has a set of radially spaced,upwardly extended, elongated outlet slots 68, 70, and 72 incommunication with the axial flow passageway 50. The outlet slots 68,70, and 72 provide a plurality of outlets to radially discharge the oiland gas feed into the bubble cap 44. The upper portion 66 of the riser42 has an upper end 74 (FIGS. 1 and 6) with an internally threadedrecess or hole 75 about its vertical axis. The top of the upper end 74has an offset, downwardly extending, vertical rectangular notch 76 whichprovides a riser keyway.

Positioned in the axial flow passageway 58 of the riser 42 is a one-wayvalve 77 (FIG. 4), such as a float valve, to accommodate upward passageof oil and gas feed while blocking and preventing downward back flow ofthe oil and gas feed in the axial flow passageway 58.

As shown in FIGS. 1, 2, and 5, the bubble cap 44 has an annular topplate 78 and an elongated annular skirt 80 which is welded to anddepends downwardly from the annular top plate about the outlets 68, 70,and 72 of the riser 42 to deflect the oil and gas feed generallydownwardly. The top plate 78 and the skirt 80 have a circular peripheryand cross section.

As shown in FIGS. 4 and 5, the annular top plate 78 has a planar or flattop surface 82 and a planar or flat bottom surface 84 which is seatedupon upper end 74 of the riser 42. The annular top plate has a circular,fastener-receiving or shaft-receiving, central opening and hole 86 toreceive the shaft 88 of the cap screw (fastener) 48. An elongated radialslot 90 extends radially outwardly from the central opening 86 of theannular plate to provide a bubble cap keyway.

The skirt 80 (FIGS. 1, 2, and 4) of the bubble cap 44 has an elongatedcircular wall 92 which annularly surrounds the upper end 74 of the riser42. The wall 92 has an upper attached end 94 which is welded orotherwise securely attached to and cantilevered from the periphery ofthe top plate 78. The lower unattached free end 96 of the wall 92 has anannular set of axially extending fins 98 which are positioned above thebubble tray 28. Positioned between the fins 98 are an annular array ofradial notches 100 which provide fluid flow discharge passageways toradially discharge and direct the flow of the oil and gas feed into thereactor. The lower end of the skirt 80 can have radially extending feet102 and 103 which provide abutment stops to engage a collar or the topportion of the bubble tray.

As best shown in FIGS. 9-11, the keeper or lock washer 46 has a planaror flat upper surface 104 (FIG. 10) and a planar or flat lower surface106 which engages and seats upon the top surface 82 (FIGS. 1, 2, and 4)of the top plate 78 of the bubble cap 44. The lock washer 46 has acircular, shaft-receiving, central hole 108 which is aligned inregistration with and has a similar diameter as the central opening 86of the top plate 78 of the bubble cap 44. The lock washer 46 has acircular periphery 110 which is positioned concentrically about thecentral hole 108. Preferably, the circumferences and the maximumdiameters of the peripheries of the lock washer 46 and the top plate 78of the bubble cap 44 are similar in size.

The lock washer 46 (FIGS. 9-11) has an enlarged arcuate base or segment112 which extends for about 85 degrees to about 95 degrees, preferablyabout 90 degrees, and provides a segmental quadrant support surface.Four bendable, locking tabs or tangs 114, 116, 118, and 120 areconnected to the base 112 and extend arcuately about the central hole108. Each of the tabs extends about 30 degrees to about 40 degrees andhas a radial center (RC). The radial center of each tab is spaced about55 degrees from the radial center of an adjacent tab. The tabs arespaced apart from each other and separated by generally trapezoidalopenings 122.

The lock washer 46 has a radial, rectangular key 124 which extendsvertically downwardly from the middle portion of the arcuate base 112.The key 124 is positioned radially outwardly of and offset from thecentral hole 108 (FIG. 1) of the keeper 46 to interlockingly engage thebubble cap keyway 90 and the riser keyway 76. The key 124 and bubble capkeyway 90 extend radially and have a similar radial span. The key 124has a much greater radial span than the riser keyway 76 to providesufficient mechanical strength and integrity of the key and to providesufficient metal for welding to the base 112.

As shown in FIGS. 1 and 4, the cap screw or bolt providing the fastener48 has an externally threaded shaft 88 and a hexagonal head 126 which isintegrally connected and secured to the top of the shaft. The externallythreaded shaft 88 threadedly engages the internally threaded upper end74 of the riser 42 and matingly engages and passes through the centralhole 108 of the keeper 46 and the central opening 86 of the top plate 78of the bubble cap 44. The head 126 of the fastener 48 has an underside128 which seats upon and compressively engages the upper surface 104 ofthe keeper 46. The head has hexagonal sides 130. Each of the hexagonalsides 130 has a face 132 which extends for about 60 degrees.

In order to prevent the fastener from rotating, one of the locking tabs114, 116, 118, or 120 is bent to extend upwardly in the axial directionaway from the key 124 to abut against and interlockingly engage one ofthe faces 132 of the head 126 of the fastener 48. Since the radialcenters of the tabs are spaced apart by 55 degrees and the faces extendabout 60 degrees, only one of the four locking tabs 114, 116, 118, or120 will be positioned flushed against a corresponding mating face ofthe head of the fastener for any given rotational position of thefastener. The bent locking tab provides a transverse locking lug orupwardly extending locking finger 134 (FIGS. 2, 4, 7, and 8).

In order to disassemble the bubble cap assembly 30 for periodicmaintenance and decoking, the bent locking tab 134 is bent in ahorizontal direction in coplanar alignment with the other tabs 114, 116,and 120 to allow counter rotation and removal of the fastener 48 andsubsequent removal of the keeper 46 and bubble cap. After decoking andcleaning, the bubble cap assembly 30 can be reassembled without furtherwelding by reinstalling the bubble cap 44, keeper 46, and fastener 48,thereafter bending the locking lug (tab) 134 upwardly andperpendicularly away from the upper surface 104 of the keeper 46 in themanner described above to lockingly abut against a mating face 132 ofthe head 126 of the fastener 48.

Among the many advantages of the novel bubble cap assembly and keeperare:

1. Ease of maintenance, decoking, and cleaning.

2. Superior reliability during installation and use.

3. Minimize damage to the bubble cap and the welds during removal andmaintenance.

4. Enhance profitability of the reactor.

5. Less downtime.

6. Easy to use and install.

7. Simple to fabricate.

8. Economical.

9. Efficient.

10. Effective.

Although an embodiment of the invention has been shown and described, itis to be understood that various modifications and substitutions, aswell as rearrangements and combinations of parts and components, can bemade by those skilled in the art without departing from the novel spiritand the scope of this invention.

What is claimed is:
 1. A bubble cap assembly for use in a reactor in ahydrocarbon processing plant, comprising:a tubular riser for injectinghydrocarbons generally upwardly in a reactor, said riser defining anotch providing a riser keyway; a bubble cap seated upon said riser inan umbrellalike manner for radially distributing the flow ofhydrocarbons in a reactor, said bubble cap defining a slot providing abubble cap keyway; a keeper comprising a lock washer having at least onebendable locking tab and a key for lockably engaging said bubble capkeyway and said riser keyway; and a fastener positioned upon said keeperand connected to said riser; and said locking tab being of a size andshape and having sufficient mechanical strength for securely engagingand locking said fastener to substantially prevent rotation and removalof said fastener during operation of said reactor.
 2. A bubble capassembly in accordance with claim 1 wherein said fastener comprises ahexagonal cap screw.
 3. A bubble cap assembly in accordance with claim 1wherein said fastener comprises a hexagonal bolt.
 4. A bubble capassembly in accordance with claim 1 wherein said bubble cap keyway issubstantially longer than said riser keyway.
 5. A bubble cap assembly inaccordance with claim 4 wherein said key has a greater span than saidriser keyway.
 6. A bubble cap assembly in accordance with claim 1wherein said key comprises an axially extending key.
 7. A bubble capassembly in accordance with claim 6 wherein said keeper has an enlargedarcuate support surface seated against and weldably secured to said keyfor enhancing the load-carrying strength and rigidity of said key, saidarcuate support surface being substantially larger than and positionedsubstantially perpendicular to said axially extending key.
 8. A bubblecap assembly for use in a reactor in an oil refinery, comprising:anelongated, upwardly extending tubular riser defining an axial flowpassageway extending generally upwardly in a reactor and an annularsidewall positioned about said axial flow passageway, said riser havinga lower portion defining at least one inlet for receiving a feedcomprising oil, an annular flange extending diametrically outwardly fromsaid sidewall for supporting a bubble tray, an upper portion defining aset of radially spaced, upwardly extending, elongated outlet slotsproviding a plurality of outlets in communication with said axial flowpassageway for radially discharging said oil, and an internally threadedupper end defining an offset downwardly extending notch providing ariser keyway; a bubble cap having an annular top plate and an elongatedannular skirt depending downwardly from said annular top plate aboutsaid outlets of said riser for deflecting said oil generally downwardly,said annular top plate and said skirt having a substantially circularperiphery, said annular top plate having a substantially planar topsurface and a substantially planar bottom surface seated upon said upperend of said riser, said annular top plate defining a substantiallycircular, fastener-receiving central opening and an elongated radialslot extending radially outwardly from said opening providing a bubblecap keyway, said skirt having an elongated circular wall annularlysurrounding said upper end of said riser, said wall having an upperattached end securely attached to and cantilevered from said peripheryof said top plate and an unattached lower free end comprising an annularset of axially extending fins defining an annular array of radialnotches providing fluid flow discharge passageways positioned above saidtray to radially discharge and direct the flow of said oil into saidreactor; an annular keeper comprising a lock washer having a generallyplanar upper surface and a generally planar lower surface for engagingand seating upon said top surface of said top plate of said bubble cap,said lock washer defining a substantially circular, shaft-receivingcentral hole aligned in registration to and having a substantiallysimilar diameter as said central opening in said top plate of saidbubble cap, said lock washer having a periphery positioned substantiallyconcentrically about said central hole and spanning a maximum diametersubstantially similar to the diameter of the circular periphery of saidtop plate of said bubble cap, said lock washer having an arcuate baseproviding an segmental quadrant support surface extending about 90degrees and having four bendable, radial, locking tabs connected to saidarcuate base and extending arcuately about said central hole, each ofsaid tabs extending about 30 degrees to about 40 degrees and having aradial center, the radial center of each tab being spaced about 55degrees from the radial center of an adjacent tab, said tabs beingspaced from each other to define generally trapezoidal openingstherebetween, said lock washer having a radial key extending downwardlyfrom the middle portion of said arcuate base and positioned radiallyoutwardly of and offset from said central hole for interlockinglyengaging said bubble cap keyway and said riser keyway; a fastenerselected from the group consisting of a cap screw and a bolt, saidfastener having an externally threaded shaft for threadedly engagingsaid internally threaded upper end of said riser and matingly engagingsaid central hole of said annular keeper and said central opening ofsaid top plate of said bubble cap, said fastener having a substantiallyhexagonal head integrally connected to said shaft, said head having anunderside for seating upon and compressively engaging said upper surfaceof said annular keeper and substantially hexagonal sides, each of saidsides having a face extending about 60 degrees; and one of said lockingtabs of said annular keeper being bent and extending upwardly in anaxial direction away from said key to provide a transverse locking lugfor interlockingly engaging and abutting against one of said faces ofsaid head of said fastener to substantially prevent said fastener fromrotating.
 9. A bubble cap assembly in accordance with claim 8 whereinsaid key and said notch are substantially rectangular.
 10. A bubble capassembly in accordance with claim 9 wherein said key and slot extendradially and have a substantially greater radial span than said notch.11. A bubble cap assembly in accordance with claim 10 wherein said keyand slot have a substantially similar radial span.
 12. A bubble capassembly in accordance with claim 8 wherein said lower portion of saidriser defines a set of upwardly extending, elongated inlet slotspositioned below said annular flange and in communication with saidaxial flow passageway.
 13. A bubble cap assembly in accordance withclaim 12 wherein said riser has a one-way valve positioned in said axialflow passageway for accommodating upward passage of oil butsubstantially blocking downward back flow of oil in said axial flowpassageway.
 14. A bubble cap assembly in accordance with claim 13wherein said lower end of said skirt of said bubble cap has radiallyextending feet providing abutment stops for engaging the top portion ofsaid bubble tray.